Mid-roller with reduced-friction guide

ABSTRACT

A mid-roller for a tracked work vehicle has a shaft and a pair of hubs assembled about the shaft, each hub having a cylindrical housing with a flange portion projecting radially outward. Each mid-roller also has a pair of metallic roller wheels mounted on the pair of hubs, each roller wheel having a radial face connected to the flange portion of its respective hub and an outer cylindrical housing symmetrical with the shaft axis defining an outer peripheral surface having an elastomeric coating bonded thereon configured to engage the inner surface of the endless track belt. Each mid-roller also has a pair of non-metallic, ring-shaped reduced-friction guides. Each roller wheel has one of said reduced-friction guides mounted thereon such that the reduced-friction guide interacts with track guide blocks such that the reduced-friction guide is configured to be the point of contact between the mid-roller and the track guide blocks.

RELATED APPLICATION

This application is a continuation application of U.S. application Ser.No. 15/550,057, filed Aug. 10, 2017, now U.S. Pat. No. 10,059,390, whichclaims the benefit of U.S. Provisional Application No. 62/114,130,entitled MID-ROLLER WITH REDUCED-FRICTION GUIDE and filed Feb. 10, 2015.

BACKGROUND OF THE INVENTION Field of Invention

This invention relates generally to a supporting mid-roller for theundercarriage of an endless track work machine and more particularly toa mid-roller having a reduced-friction guide positioned between theguide blocks of an endless track and an inner shoulder of themid-roller.

Description of Related Art

A typical rubber-tracked work machine utilizes a propulsion system inwhich a continuous flexible rubber belt is frictionally driven as it isentrained about a pair of wheels. The work machines are configured tomaintain adequate tension on the endless belt around the entrainedwheels, and to keep the belt in lateral alignment with the wheels whenthe wheels are subject to large lateral loads. Tracked work machinesutilize multiple mid-rollers to distribute the vehicle's weight withinthe track and to help constrain the track from sliding off the wheelslaterally. Typical mid-rollers utilize a steel or iron wheel with anelastomer bonded to the outside surface to provide cushioning and debrisrejection. The inside metal edge of the mid-roller provides a contactsurface to engage rubber track guide blocks on the inside surface of theendless belt whenever the track wanders laterally from center.

A common problem with endless track work machines utilizing continuousflexible rubber belts is heat. Heat is generated when the rubber beltscome into contact with other drive components, such as the supportingmid-rollers, the drive wheel and the idler wheel. This is most prevalentwith the supporting mid-rollers because of the speed at which theyrotate in contrast to the drive and idler wheels, due to the supportingmid-roller generally being smaller in diameter.

High speed roading and field operation on slopes are two typicalconditions that result in significant rubbing of the mid-roller edgeswith the track guide blocks. Due to the friction created between theedge of a steel or iron mid-roller and a rubber track guide block,substantial heat may be generated in both the midroller and guideblocksfrom this sliding contact. U.S. Pat. No. 6,299,264 issued to Kautsch etal. describes a mid-roller having a heat shield that is positionedbetween mid-roller segments and the guide blocks. The heat shield isintended to insulate the midroller from the heat generated bymetal-to-rubber contact with the guide blocks. However, this design doesnothing to reduce the amount heat that is also built up in the guideblocks. Since excess heat can quickly deteriorate the bond betweenmid-roller wheels and their elastomer coating, in addition todeteriorating the rubber guide blocks, it would be desirable to reducethe overall friction from this interface.

OVERVIEW OF THE INVENTION

In one embodiment, the invention is directed to a tracked work machinehaving a track roller assembly. The track roller assembly includes adrive wheel, an idler wheel, and an endless track belt disposed aboutthe drive and idler wheels. The endless track belt is at least in partmade of a rubber material and defines an inner surface, a groundcontacting outer surface, and a pair of edges. The endless track beltalso has a track guide block positioned on the inner surface between thepair of edges. The track roller assembly has at least one supportingmid-roller located between the drive wheel and the idler wheel andconfigured to engage the guide block to aid in maintaining alignment ofthe endless track belt. The at least one mid-roller includes acylindrical shaft defining a shaft axis extending to outer ends of theshaft and a pair of roller wheels, with one of the pair of roller wheelsmounted on each of the outer ends of the cylindrical shaft. Each rollerwheel has a radial face connected to the respective outer end of thecylindrical shaft and an outer cylindrical housing symmetrical with theshaft axis defining an outer peripheral surface having an elastomericcoating bonded thereon configured to engage the inner surface of theendless track belt. Each roller wheel further defines an inner shoulderhaving a recess formed therein, wherein the roller wheel has at leastone rib extending radially inward from the outer cylindrical housing,with the at least one rib having a step formed in an inward surface. Theat least one mid-roller also includes a pair of non-metallic,ring-shaped reduced-friction guides, wherein each roller wheel has oneof said reduced-friction guides pressed into the recess on the innershoulder of the roller wheel with a snap fit engagement with the step ofthe at least one rib. The reduced-friction guide interacts with thetrack guide block such that the reduced-friction guide is configured tobe the frictional point of contact between the mid-roller and the trackguide block.

These and other features and advantages of this invention are describedin, or are apparent from, the following detailed description of variousexemplary embodiments of the systems and methods according to thisinvention.

BRIEF DESCRIPTION OF THE DRAWINGS

The above mentioned and other features of this invention will becomemore apparent and the invention itself will be better understood byreference to the following description of embodiments of the inventiontaken in conjunction with the accompanying drawings, wherein:

FIG. 1 is a side elevational view of a work machine embodying thepresent invention;

FIG. 2 is an enlarged sectional view of a mid-roller of the presentinvention taken along line A-A of FIG. 1;

FIG. 3 is a perspective view of a roller wheel with a reduced-frictionguide;

FIG. 4 is perspective view of the roller wheel with the reduced-frictionguide removed; and

FIG. 5 is a perspective view of the reduced-friction guide.

Corresponding reference characters indicate corresponding partsthroughout the views of the drawings.

DETAILED DESCRIPTION OF EXEMPLARY EMBODIMENTS

The invention will now be described in the following detaileddescription with reference to the drawings, wherein preferredembodiments are described in detail to enable practice of the invention.Although the invention is described with reference to these specificpreferred embodiments, it will be understood that the invention is notlimited to these preferred embodiments. But to the contrary, theinvention includes numerous alternatives, modifications and equivalentsas will become apparent from consideration of the following detaileddescription.

Referring initially to FIG. 1, a work machine 10 has a pair of trackroller assemblies 12, only one shown, configured to drive the workmachine over ground. Each track roller assembly 12 includes a drivewheel 14 and an idler wheel 16 with an endless rubber track belt 18disposed about the drive and idler wheels 14, 16. In as much as thetrack roller assemblies 12 are substantially structurally andoperatively similar, further reference will be made to only a singleside of the work machine 10. In this example, an engine (not shown)powers the drive wheel 14, in a conventional manner, and frictionallydrives each of the endless rubber belts 18. Located between the drivewheel 14 and the idler wheel 16 is a plurality of supporting mid-rollers30. The mid-rollers 30 are attached to a track roller frame 32 in anymanner known in the art. The work machine 10, for example, is anagricultural tractor positioning the drive wheel 14 near the back andthe idler wheel 16 toward the front of the work machine 10.

Referring now to FIG. 2, the endless rubber belt 18 defines an innersurface 34, a ground contacting or outer surface 36, and a pair of edges38. Positioned on the inner surface 34 and centrally located between thepair of edges 38 is a plurality of guide blocks 40.

Each mid-roller 30 includes a cylindrical shaft 44 defining an axis 46extending to outer ends 48. Assembled about the cylindrical shaft 44 isa pair of hubs 50 being symmetrical with the axis 46 of the cylindricalshaft 44. Each hub 50 includes a cylindrical housing 52 spaced from theaxis 46 a predetermined distance and defining an outer surface 54. Thecylindrical housing 52 defines a first end 56 positioned inwardly of therespective one of the outer ends 48 of the shaft 42 and a second end 58positioned outwardly of the same respective one of the outer ends 48.Progressing from the first end 56 to the second end 58 is a firstbearing 60, a spacer 62 and a second bearing 64. Spaced inwardly andprojecting radially outward from the second end 58 is a flange portion66 having a plurality of holes positioned therein. Positioned at thesecond end 58 of each cylindrical housing 52 is a roller wheel 70. Eachroller wheel 70 has a radial face 72. A plurality of fasteners 74connects the respective roller wheel 70 using the holes in the flangeportion 66 of the hub 50. An outer cylindrical housing 76, symmetricalwith the axis 46, extends axially inwards from the radial face 72towards a center axis 78 of the mid-roller 30 and forms an innershoulder 80. The outer cylindrical housing 76 has an outer peripheralsurface 82. An elastomeric coating 84, for example rubber, is bonded tothe outer peripheral surface 82.

Turning also now to FIGS. 3-5, according to the invention, a ring-like,reduced-friction guide 90 is mounted to the portion of the roller wheel70 interacting with the track guide blocks 40. In one embodiment, thereduced-friction guide 90 is pressed into a cast or machined recess onthe inner shoulder 80 of the roller wheel 70. The reduced-friction guide90 is configured to be the point of contact between the mid-roller 30and the track guide blocks 40 during high speed roading and fieldoperation on slopes, which result in significant rubbing of themid-roller 30 with the track guide blocks 40.

In one desirable embodiment, the roller wheel 70 has a plurality of ribs92 extending radially inward from the outer cylindrical housing 76. Eachrib 92 has a step 94 formed in an inward surface with a recess 96 behindthe step 94. The reduced-friction guide 90 has a circumferential tongue98 with a catch 100 at the end of the tongue 98. The reduced-frictionguide 90 is pressed against the inward shoulder 80 such that the tongue98 deflects over the step 94 in each rib 92 causing the catch 100 tosnap fit into the recess 96. However, one skilled in the art willunderstand that the reduced-friction guide 90 could be held into placeby other methods, such as bonding or mechanical fastening.

The reduced-friction guide 90 is made of a non-metallic materialdissimilar with the material of the roller wheel 70. Desirably, thereduced-friction guide 90 is molded of plastic. As is customary in theart, the roller wheel 70 is desirably made of steel or iron. Due to thefriction created between the mid-roller 30 and the rubber track guideblock 40, heat is generated from the sliding contact. Based on theassumption that the coefficient of friction between smooth steel or ironand rubber is approximately 0.5 and that some non-metallic materials canachieve a coefficient of friction of approximately 0.15 with rubber,adding the reduced-friction guide 90 of non-metallic material can reduceheat generation from the sliding friction. Desirably, the non-metallicmaterial is a plastic material having good heat and abrasion-resistingproperties. One suitable plastic material for the reduced-friction guide90 is Ultra High Molecular Weight Polyethylene (UMHW-PE).

An additional benefit of the reduced-friction guide 90 is that thethermal properties of non-metallics (plastics) tend to be poorconductors of heat, compared to metals. Therefore, whatever heat may begenerated by the reduced-friction guide 90 will be slow to propagate tothe metal roller wheel 70 and its elastomeric coating 84.

The foregoing has broadly outlined some of the more pertinent aspectsand features of the present invention. These should be construed to bemerely illustrative of some of the more prominent features andapplications of the invention. Other beneficial results can be obtainedby applying the disclosed information in a different manner or bymodifying the disclosed embodiments. Accordingly, other aspects and amore comprehensive understanding of the invention may be obtained byreferring to the detailed description of the exemplary embodiments takenin conjunction with the accompanying drawings.

1. A tracked work machine having a track roller assembly comprising: adrive wheel; an idler wheel; an endless track belt disposed about thedrive and idler wheels, the endless track belt at least in part made ofa rubber material and defining an inner surface, a ground contactingsurface, and a pair of edges, wherein the endless track belt comprises atrack guide block positioned on the inner surface between the pair ofedges; at least one supporting mid-roller located between the drivewheel and the idler wheel and configured to engage the guide block toaid in maintaining alignment of the endless track belt, the at least onemid-roller comprising: a cylindrical shaft defining a shaft axisextending to outer ends of the shaft; a pair of roller wheels, with oneof the pair of roller wheels mounted on each of the outer ends of thecylindrical shaft, each roller wheel having a radial face connected tothe respective outer end of the cylindrical shaft and an outercylindrical housing symmetrical with the shaft axis defining an outerperipheral surface having an elastomeric coating bonded thereonconfigured to engage the inner surface of the endless track belt,wherein each roller wheel further defines an inner shoulder having arecess formed therein, wherein the roller wheel has at least one ribextending radially inward from the outer cylindrical housing, with theat least one rib having a step formed in an inward surface; and a pairof non-metallic, ring-shaped reduced-friction guides, wherein eachroller wheel has one of said reduced-friction guides pressed into therecess on the inner shoulder of the roller wheel and in engagement withthe step of the at least one rib, the reduced-friction guide interactingwith the track guide block such that the reduced-friction guide isconfigured to be the frictional point of contact between the mid-rollerand the track guide block.
 2. The tracked work vehicle of claim 1wherein the reduced-friction guide is symmetrical about the axis of thecylindrical shaft.
 3. The tracked work vehicle of claim 1 wherein eachof the pair of reduced-friction guides comprises a pre-formed plasticpiece adapted to be snap-fit into the recess on the inner shoulder ofthe roller wheel.
 4. The tracked work vehicle of claim 1 wherein theroller wheel has a plurality of ribs extending radially inward from theouter cylindrical housing and each rib has a step formed in an inwardsurface with a second recess behind the step, and the reduced-frictionguide has a circumferential tongue with a catch at the end of thetongue, the tongue configured to deflect over the step in each ribcausing the catch to snap fit into the second recess when thereduced-friction guide is pressed against the inner shoulder.
 5. Thetracked work vehicle of claim 4 wherein the second recesses and the ribsof each roller wheel act to secure the reduced-friction guide bothaxially and laterally on the roller wheel.
 6. The tracked work vehicleof claim 1 wherein the reduced-friction guide is molded of plastic andthe roller wheel is made of either steel or iron.
 7. The tracked workvehicle of claim 6 wherein the reduced-friction guide is made of UltraHigh Molecular Weight Polyethylene (UMHW-PE).
 8. The tracked workvehicle of claim 1 wherein the outer cylindrical housing of each rollerwheel has an inner peripheral surface, the inner shoulder defined on theinner peripheral surface.